With reference to relevant studies, to what extent does genetic inheritance influence behaviour?

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Genetics and behaviour

With reference to relevant studies, to what extent does genetic inheritance influence behaviour?

Research has shown that to a certain extent genetic inheritance does indeed influence behaviour; however, one must take into account the environmental factors in order to address this issue in its entirety. Adoption and twin studies are commonly used in genetic research as these allow the most direct comparison of genetic and environmental influence of behaviour. Genes determine characteristics in a person and are passed down through generations; however, the environment can influence these characteristics, for example the effect of nutrition and weight. So the question remains as to which have a stronger influence, genetic inheritance or the environment.

Monozygotic (MZ) twin studies are widely accepted in genetic research. They enable us to research the effects of genetics on behaviour because the genes of MZ twins are virtually identical. A study to support the relationship between genetic inheritance and behaviour is the Minnesota Twins study (Bouchard, 1990), which aimed to observe the effect of environment and genetic inheritance upon a multitude of factors which included: intelligence quotient, personality and occupational/vocational interests, by investigating the correlation between these factors in twins reared apart using MZT's as a control.  Monozygotic twins reared together or apart, from all over the world, were compared and undertook 50 hours of medical testing and interviews. Their results showed that 70% of intelligence can be attributed to genetic inheritance (intelligence correlations of: r(MZA's) = 0.71; r(MZT's)=0.79), the rest to environmental factors. Strengths in the methodology included a large, multicultural [[sample size and unlike previous research the adult population was addressed. However, recruitment relied on media coverage and there are ethical concerns about how the twins were reunited. There was also no control of previous contact between the twins and there was an assumption made that the twins reared together lived in an equal environment. Despite these weaknesses the study does show a strong correlation between genetic inheritance and intelligence, suggesting that genetic inheritance has a substantial influence on behaviour.

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Heston, in 1966, conducted an investigation to test to what extent schizophrenia is due to genetic factors. The aim of this experiment was to figure out whether schizophrenia was more influenced by genetics or the environment. This was done by conducting an adoption study, where 47 adults who were adopted yet had biological mothers who had schizophrenia or some form of mental illness and 50 healthy, adopted adults (control) were tested and compared. The results showed that 10% of the adults with schizophrenic mothers were diagnosed with schizophrenia, while no one in the control group was diagnosed with schizophrenia. ...

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